1. Field of the Invention
The invention mainly discloses a semiconductor light emitting device, particularly discloses a semiconductor light emitting device having an insert layer.
2. Description of the Prior Art
Please refer to FIG. 1, which shows the structure of a conventional semiconductor light emitting device 100, which includes: a substrate 102; a first semiconductor conductive layer 104 is disposed on the substrate 102; an active layer 106 is disposed on the first semiconductor conductive layer 104; an electron blocking layer 108 is disposed on the active layer 106; a second semiconductor conductive layer 110 is disposed on the electron blocking layer 108, in which the electric of the second semiconductor conductive layer 110 is opposite to that of the first semiconductor conductive layer 104; a first electrode 122 is disposed on the second semiconductor conductive layer 110; and a second electrode 124 is disposed on another surface of the substrate 102.
As shown in FIG. 2, for the structure of another conventional semiconductor light emitting device 200, which includes: a substrate 202; a first semiconductor conductive layer 204 having a first part (not shown in the figure) and a second part (not shown in the figure) which are disposed on the substrate 202; an active layer 206 is disposed on the first part of the first semiconductor conductive layer 204; an electron blocking layer 208 is disposed on the active layer 206; a second semiconductor conductive layer 210 is disposed on the electron blocking layer 208, in which the electric of the second semiconductor conductive layer 210 is opposite to that of the first semiconductor conductive layer 204; a first electrode 222 is disposed on the second semiconductor conductive layer 210; and a second electrode 224 is disposed on the second part of the first semiconductor conductive layer 204, in which the electric is separated from the element on the first part of the first semiconductor conductive layer 204.
From the above-mentioned structure, it is known that the use of broad energy gap semiconductor material as the carrier blocking layer 108, 208 has become very common application in the semiconductor light emitting device 100, 200, such as laser diode and light emitting diode. However, it is mentioned in the prior art, utilizing certain amount of aluminum gallium nitride as the electron blocking layer 108, 208 can reduce the overflow of electron greatly. Also, the electron blocking layer will influence the electron hole 108, 208, it will be more difficult to inject into the active layer 106, 206. While in the other prior art, the P-type gallium nitride layer using gradually change doping concentration can influence the advancing behavior of carrier in energy band diagram. As shown in FIG. 3, in the other prior art, it is mentioned that utilizing the quantum energy barrier with super lattice can further prevent the overflow of the electron. However, even the above-mentioned methods can prevent the overflow of the electron successfully, it will increase the difficulty for injecting the electron hole into the active layer 106, 206, and it will become harder to manufacture the light emitting device.
Refer to FIG. 4, when the conventional light emitting device is operated under forward bias, the valance electron band diagram of electron blocking layer will be triangular shape, due to the factor of internal polarization field and forward bias. The valance electron band of electron blocking layer is declined upwards from the conductive layer of N-type semiconductor conductive layer to P-type semiconductor conductive layer, which blocks the transmission ability of electron hole passing through this triangular blocking layer. However, if the aluminum content is increased from P-type semiconductor conductive layer to N-type semiconductor conductive layer in electron blocking layer, the band-gap will be increased gradually. Thus, when the slope of valance electron band is increased, the barrier in valance electron band will become flat and maybe overturned.